How you back up Capture One depends on one choice you made at import, often without noticing: whether your images live inside the catalog or are referenced from where they already were. Capture One's built-in catalog backup protects your edits, ratings, and keywords. It doesn't copy referenced images, and on most photographers' Macs that's nearly every RAW file they own.
So a full Capture One backup has two halves. The catalog (or session) holds the work you did. The image folders hold the photos. Each needs its own copy on another drive.
TL;DR: Capture One's Catalog Backup (Preferences → General) copies the catalog's database: adjustments, ratings, keywords, albums. It does not copy referenced images, which is where most RAW files live. Set the backup location to a folder outside the catalog, then back up that folder and every image folder the catalog references to a second drive or the cloud. Sessions are plain folders, so back up the whole session folder.
Catalog or session: which one are you using?
Capture One has two ways to organize work, and they back up differently.
A catalog is a single .cocatalog package that tracks images from many shoots, wherever they live. It's the Lightroom-style setup, and most photographers who don't shoot tethered in a studio use one.
A session is a folder per job with a fixed structure: Capture, Selects, Output, and Trash subfolders plus a .cosessiondb file. The images live inside the session folder, and each image's adjustments are saved in small settings files next to it. Studio and tethered shooters tend to use sessions, one per client or shoot.
If you see one big package in Finder that grows over the years, you're on a catalog. If you see a folder per job with Capture inside, you're on sessions.
What's inside a Capture One catalog, and what isn't
Open a .cocatalog in Finder with right-click → Show Package Contents and you'll find the catalog database (the .cocatalogdb file with every adjustment, rating, keyword, and album), cache folders with previews and thumbnails, and, only if you chose it at import, the image files themselves.
That last part depends on the Store files setting in the import dialog:
- Inside catalog copies images into the package. The catalog is then self-contained and large.
- Current location, or a folder you pick, leaves images on disk where they are and references them. The catalog stays small, and the RAWs live on your Mac or, more often, on external drives.
Most catalogs are referenced or a mix of both, because nobody wants a 4TB package on their internal SSD. That's why "I back up my catalog" so often means "I back up my edits, and the photos are on one drive."
How to set up Capture One's catalog backup
Go to Capture One → Settings (Preferences) → General, and find Catalog Backup.
- Set Backup frequency. Daily or weekly suits most people. Capture One runs the backup when you close the catalog, so a once-a-day setting means "the first time you quit each day."
- Set Backup location to a folder outside the catalog package, for example
~/Pictures/Capture One Backups. Pick a folder you'll include in your regular backup, because this setting decides where your edits end up as files. - To back up right now, use File → Back Up Catalog.
Each backup is a copy of the catalog database at that moment. To roll back, open the backup with File → Open, check that it's the state you want, and keep working from it (or copy it over the damaged catalog once Capture One is closed).
What Capture One's backup leaves out
The catalog backup is good at one thing: rolling back a catalog that got corrupted, or edits you regret. It doesn't help in three common situations.
A dead image drive. Referenced RAWs aren't in the backup. If the drive holding 2025/Weddings dies, the catalog still shows previews of every image and knows every adjustment, but the originals are gone, and you can't export full-resolution files from previews.
A dead Mac. The backup location is usually on the same Mac as the catalog. One failed SSD takes the catalog and its backups together.
Previews and cache. These aren't backed up, which is fine, since Capture One rebuilds them from the originals. It just means a restored catalog needs time to regenerate thumbnails.
How to back up a Capture One session
Sessions are easier. Everything a session needs lives in its folder: the images, the .cosessiondb, and per-image settings in the CaptureOne subfolders next to the images. Copy the whole session folder and you have the job, edits included.
The common mistake is backing up only Output (the delivered JPEGs) or only Selects. The client files survive, but the RAWs and adjustments behind them don't. Back up the session folder from its top level.
Close the session before copying it by hand, so the session database isn't mid-write.
What happens when images are on a drive that isn't plugged in
Capture One marks referenced images as offline when their drive isn't connected. You can still browse previews, read metadata, and change ratings and keywords, but you can't edit or export at full quality until the drive is back. Folders whose drive is missing show up in the Library with a question mark, and Locate lets you point Capture One at the new location if you moved or renamed them.
This is where multi-drive setups get fragile. The catalog knows which folder each image came from. It doesn't know whether a second copy exists, which drive in the drawer has it, or whether that copy is intact.
Getting edits and RAWs onto a second drive
You need three things copied off the Mac: the catalog backup folder (or each session folder), every image folder the catalog references, and ideally one copy offsite.
Time Machine covers the catalog and backups if they're on your internal drive. It ignores external drives by default, which is usually where the referenced RAWs are.
Carbon Copy Cloner or ChronoSync can mirror each image drive to a second drive on a schedule. That works when one photo drive maps to one backup drive.
Tusk fits when RAWs are spread across several drives and you want to know which drive holds which shoot without plugging them all in. Add the Capture One backup folder as one Tusk project and each image folder (or each year's folder) as another, then add backup destinations, for example a second external drive and an Amazon S3 bucket. Tusk copies new and changed files to every destination, verifies each copy with a BLAKE3 checksum, and shows per-file status even while drives are unplugged. Its Delete local action removes RAWs from your Mac only after every destination has a verified copy. Capture One then shows those images as offline until you plug the drive back in or restore them.
Two limits, plainly: Tusk doesn't read the Capture One catalog, so it backs up files, not edits as such. Back up the catalog backup folder, not the live catalog package while Capture One has it open. And Tusk doesn't relink images inside Capture One. If you move folders, use Capture One's Locate.
FAQ
Only images stored inside the catalog. The catalog backup copies the catalog database, which holds adjustments, ratings, keywords, and albums. Referenced images, the ones you left in their current location at import, are not part of the backup and need to be copied to another drive separately.
In the folder set as Backup location under Capture One → Settings → General → Catalog Backup. Set it to a folder outside the catalog package that your regular backup includes. Because that folder is on your Mac by default, also copy it to an external drive or cloud destination.
Open the backup with File → Open in Capture One and check that it contains the edits you expect. Then either keep working in it or, with Capture One closed, replace the damaged catalog with the backup copy. Previews and thumbnails rebuild from the original images, so referenced image drives need to be connected for full quality.
Catalogs suit photographers who manage years of work in one place and keep RAWs on external drives. Sessions suit job-based and tethered work, since each session is a self-contained folder that backs up and hands over as one unit. For backup, sessions are simpler: copy the folder. Catalogs need the catalog backup plus every referenced image folder.
The drive or folder holding the referenced originals isn't available. Usually the external drive is unplugged, or the folder was renamed or moved in Finder. Reconnect the drive, or use Locate in the Library to point Capture One at the folder's new location. You can browse previews while images are offline, but not edit or export at full quality.
Not on its own. A session folder contains everything the job needs, but it's still one copy on one drive. Copy the whole session folder (not just Output or Selects) to at least one other drive, and ideally one offsite or cloud destination.